1. Field of the Invention
This invention relates to a system for sensing the configuration of a path on a workpiece in front of an operating mechanism movable along the workpiece and for controlling the direction and rate of motion of the operating mechanism with respect to the path.
2. Prior Art
A variety of position control systems have been devised to control the motion of an operating head such as a cutter, welder, flame cutter or the like along a path on a workpiece to be operated upon. If the path can be conveniently defined in numerical terms a program can be prepared in advance for generating the appropriate control signals to achieve the desired motion. However, it is often inconvenient to thus define the path, or as in the case of a pair of abutting plates that are to be welded together, no two paths are identical so that the cost of preparing a unique program for each set of parts cannot be justified. Various forms of line-following control systems have been devised for this latter class of applications. These systems include sensors which detect the path to be followed such as the line of abutment between a pair of plates to be welded, or a line marked on a workpiece, and provide signals to a position control system operative to move the operating mechanism along that path. These units may employ any of a wide variety of sensors such as capacitive, magnetic or optical devices depending upon the nature of the path. Typically they include a pair of sensors which straddle the path and develop a differential signal used to determine the relative position of the operating mechanism and the path.
These devices employ servo drives which sense the deviation between the path being followed and the motion of the operating mechanism and modify the operating mechanism in such a direction as to minimize the difference.